1. Field of the Invention
The present invention relates to an improved brush holder for an electrical machine, and in particular to a brush holder for an electric motor for power tools.
2. Description of the Prior Art
Brush holders for electrical machines are known in manifold forms from the prior art. For instance, in universal electric motors of the kind typically used in power tools, such as right-angle sanders, power drills, and the like, the necessary current reversal (commutation) is effected with the aid of a commutator. The transmission of the current to the commutator is done by means of carbon brushes. These carbon brushes are disposed in a brush holder, which must furnish exact guidance of the brush and a necessary, metered contact pressure. From Swiss Patent Disclosure CH 493 115, a brush holder is known in which prestressing is exerted on the brushes by means of a spring tongue and a tension spring. Between the brush and the pressure tongue, a cylindrical contact-pressure member is provided, which presses into a V-shaped notch in the carbon brush, in order to exert a uniform contact pressure on the brush.